| Number | Date | Country |
|---|---|---|
| 0251180 | Jan 1988 | EPX |
| 2742616 | Mar 1979 | DEX |
| 2824205 | Dec 1979 | DEX |
| 663897 | Aug 1929 | FRX |
| 1286368 | Jan 1962 | FRX |
| 42-18757 | Sep 1967 | JPX |
| 0009914 | Jan 1978 | JPX |
| 57-206530 | Dec 1982 | JPX |
| 354880 | Aug 1931 | GBX |
| Entry |
|---|
| "Pipe Processing Method", pp. 132-133, published Sep. 30, 1982. |